Legal Api: Update error handling on invalid DATE format (Or other query params)

* Originally there was an 500 response from the API when a GET request was made to retrieve DIRECTORS but with a bad DATE format.
* This ticket is to update the api's handling of that query param to give an accurate response due to invalid formatting in the DATE or other potential query param's.
* Validate the date format on the backend for directors and addresses endpoints (and any others that take query params), and return correct error response.

UI work to fix this has already been completed.